THE NEOGENE EVOLUTION OF THE OUTER CARPATHIAN FLYSCH UNITS (POLAND, UKRAINE AND ROMANIA) - KINEMATICS OF A FORELAND FOLD-AND-THRUST BELT SYSTEM

Various techniques of geometric and kinematic analyses, including cross-section balancing and forward modeling, have been applied successfully to the outer Carpathian flysch units along regional geologic profiles crossing the belt from its undeformed foreland to the Pieniny klippen belt (western Carpathians, Poland) or to the central east Carpathian allochthon (eastern Carpathians, Ukraine and Romania). The amounts of Neogene shortening as well as the mode and the location of basement consumption are discussed on the basis of balanced cross-sections compiled along the three most representative regional traverses. In addition, the complete kinematic evolution of complex Carpathian structures, such as the Fore-Dukla triangle zone (southeastern Poland), the Borislav-Pokut duplexes (Ukraine) and the Marginal Folds (Romania) are described in more detail by using a forward modeling approach. Major results concern the tectonic heritage of Laramian inverted structures (Mesozoic normal faults reactivated as reverse faults during the Late Cretaceous-Paleocene compression or transpression) in the development of the Neogene outer Carpathian edifice. Pre-Eocene deformation and erosion effectively induce discontinuities in the Mid-Cretaceous blackshale detachment horizon, and help to localize the Neogene deformations in complex triangle zones. The thrust sequence itself evolves alternatively in a piggyback or in an out-of-sequence mode. Clearly, the critical taper of the outer Carpathians is preserved by a constant balance between erosion and thrust reactivations in the inner part of the wedge, and sedimentation and tectonic accretion at its front.